This proposal deals with the structure, expression and functional role(s) of each of the six actin genes of the actin multigene family, the single calmodulin gene, and the vimentin gene(s) of Drosophila melanogaster. Using specific probes for each of these genes, we propose to investigate the timing, size and possible hormonal triggering of the transcript from each of these genes by hybridization to "dots" of unfractionated RNA, "Northern blots" of polyA RNA, and tissue section RNAs. These isolated RNAs will be taken from different stages of development, from certain mass isolated tissues, such as imaginal discs and from Drosophila discal neoplasms. The cytological sections will represent Drosophila ovaries, embryos, larvae, pupae and adults in order to investigate the timing and tissue specificity of each gene. Mutants at each locus will be selected in order to correlate the expression of a transcript with the functional role(s) of its product in the organism. Putative calmodulin mutants will be fed phenothiazines as a selective tool. Transformation experiments are described to investigate the physiological specificity of each actin polypeptide. These experiments are designed to define the relationships between individual members of the actin multigene family, the calmodulin gene, and the vimentin gene(s) during development and in certain D. melanogaster neoplasias.